1. Field of Invention
The present invention relates to a method of checking the location of moving parts in a machine, and to apparatus for carrying out the method.
2. Description of Prior Art
British Pat. No. 1,545,656 (General Electric Company of New York State, U.S.A.) discloses a microwave proximity detector which is especially useful for measuring the clearances between tips of rotating turbine blades and the casing of a jet engine. In the detector, microwaves are propagated to a microwave junction to produce propagating reflected waves on one side of the junction and an evanescent electromagnetic field on the other side of the junction. Turbine blades on the said other side perturb the evanescent field and vary the reflection of the propagating waves to produce an indication of the clearance.